Control law design for the air-turbine-generator set of a fully submerged 1.5 MW mWave prototype. Part 2: Experimental validation.

A fully-submerged bottom-standing 1.5 MW wave energy converter (WEC) equipped with a membrane-pump system is being developed for installation at a test site off the coast of Pembrokeshire, Wales, UK. The system comprises several flexible-membrane air-cells that are compressed and sucked by the action of the waves, a system of rectifying valves, low-pressure and high-pressure ducts and a unidirectional air turbine that drives an electrical generator. This two-part paper reports the design and testing of an effective control law to be implemented into the programmable logic controller of the membrane-pump turbine-generator set, allowing efficient and safe operation for the wave climate at the Pembrokeshire test-site. Part 2 of this paper focuses on the experimental investigation at the IST variable flow test rig of the real-time control algorithm described in Part 1 of this paper, using a 1:2.4 turbine scale model. Tests were performed for five sea-states and two turbine model average rotational speeds. Experimental results reveal that the control law proposed for the Pembrokeshire mWave turbine-generator set, based only on the turbine rotational speed and airflow density measurements, is effective and of a simple implementation. Fine fitting between the model testing results validates the performed scaling of the variables related to the time-dependent turbine-generator operation, as well as the numerical model of the system described in Part 1. • The turbine-generator set real-time control algorithm was experimentally studied. • Tests were performed for five sea-states and two turbine model average rotational speeds. • The control law based on the turbine rotational speed and airflow density is effective. • Model testing results validate the scaling of the turbine-generator operation time-dependent variables. [ABSTRACT FROM AUTHOR]